I've the following situation: Phone A: Codec GSM supported Phone B: Codec iLBC supported in sip.conf: [general] ... disallow=all allow=gsm allow=ilbc allow=alaw allow=ulaw canreinvite=yes ... (There's a lot of other SIP users, that's why I made the default codec list bigger than just GSM and/or ALAW) If phone A calls to phone B the conversation is established at SIP level, but there's no RTP traffic between the machines. If I make a "sip show channels at the Asterisk console, I see: server*CLI> sip show channels Peer User/ANR Call ID Seq (Tx/Rx) Form Hold Last Message 192.168.1.101 phone_A 10095d01445 00103/00000 ulaw No Tx: ACK 192.168.1.107 phone_B 182E175F-F6 00102/00002 ulaw No Tx: ACK 2 active SIP channels (ULAW?!?!?, not even ALAW!!!) As far as I understand, since in this case the communication can not be established directly between A and B (i.e. bypassing Asterisk as the media transport), given the fact that the A codec and the B codec are different, the REINVITE shouldn't be issued and discarded automatically for Asterisk, even and despite the fact canreinvite=yes is set. However, it seems to be issued anyway, so I can't hear anything. Am I doing something wrong, or this is effectively an Asterisk problem? Asterisk 1.2.4 SIP Client: SJPhone 1.60.289a I checked the REINVITE sent from Asterisk to the phones with Ethereal. Also, if I set canreinvite=no, the communication works nice, with GSM for one side and iLBC in the other. Thanks a lot for your attention. -- Atly. Alvaro Palma